Slow positron applications at slow positron facility of institute of materials structure science, KEK

Positronium is a bound state of one electron and one positron. It can be seen as the lightest neutral “atom”. It can also be seen as a neutralized electron or a neutralized positron. Since positronium is electrically neutral, special techniques are required to generate a variable energy beam of positronium. In recent years, it has become possible to efficiently generate positronium negative ions in which another electron is bound to positronium. It is possible to generate an energy-tunable positronium beam by accelerating positronium negative ions with an electric field and irradiating them with laser light to photodetach one electron. Generation of such a positronium beam has actually been realized, and applied research has begun. Here, we describe the energy-variable positronium beam generation, its applied research including the observation of the motion-induced resonance of positronium and the first measurement of the binding energy of positronium to one electron.

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“…A Ps beam using (a) was built at the High Energy Accelerator Research Organization (KEK), in Tsukuba (Japan) [123]. Figure 11 shows the setup.…”

Section: Energy-tunable Ps Beam Produced Using Ps − Photodetachmentmentioning

confidence: 99%

An energy-tunable positronium beam produced via photodetachment of positronium negative ions and its applications

Nagashima¹,

Michishio²,

Chiari³

et al. 2021

J. Phys. B: At. Mol. Opt. Phys.

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Challenges and advances of positronium Bose-Einstein condensation

Mondal

2019

AIP Advances

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While scientists in the USA have accomplished Bose-Einstein Condensation (BEC) of inert gas and alkaline atoms successfully, a challenging question comes into the other’s mind why not BEC of Positronium (Ps), even though, its lowest lifetime (142 ns)? A few auspicious methods of having BEC were invented and successfully applied in the atoms of infinite lifetime. But in case of Ps-BEC laser cooling is considered to be the best method provided we can meet the requisite parameters. Using the medium range e+ beam intensity we explored some solid surfaces for the laser cooling of Ps but Ps-BEC could not be achieved. Because the intensity of pulsed beam was not enough to have the phase space density, outgoing Ps from the surface with thermal motion could not be controlled inside the scattering chamber and laser-Ps interaction was without synchronization. Hence, scientists of different laboratories have been searching materials of high density Ps production, intense pulsed e+ beam, advanced detector and image reconstruction techniques. Recently we have developed calumnious silicon nano-wires of various diameters and found the signature of a long-life component of Ps and estimated the Ps production density about 1015 Ps/cm3. It is an ideal case for the achievement of the Ps-BEC. The details of these systems are explained in the following sections.

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Efficient positron trapping and extraction with a center-hole SiC remoderator

et al. 2022

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Trapping technologies of positrons, the antimatter counterpart of electrons, are indispensable for various atomic, molecular, and optical experiments and for material analyses that use positron swarms. Efficient trapping of high-intensity positron beams generated by electron linear accelerators (LINACs) will improve the quality and throughput rate of experiments but have yet to be practically realized. In the present work, we demonstrate the efficient trapping and extraction of a LINAC-based positron beam by using a silicon carbide (SiC) remoderator with a centre hole. The positron beam was remoderated by 4H-SiC wafers in the back-reflection geometry followed by accumulation in an electromagnetic trap with CF4 cooling gas. A rotating electric field was driven to spatially compress the accumulated positrons, enabling the lossless extraction of the positrons through the SiC hole. A trapping efficiency in the higher 20% range was achieved. The proposed trapping scheme employing a centre-hole SiC remoderator is thus a practical technique to accumulate and cool positron beams generated by LINACs.

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Slow positron applications at slow positron facility of institute of materials structure science, KEK

Cited by 4 publications

References 50 publications

An energy-tunable positronium beam produced via photodetachment of positronium negative ions and its applications

An energy-tunable positronium beam produced via photodetachment of positronium negative ions and its applications

Challenges and advances of positronium Bose-Einstein condensation

Efficient positron trapping and extraction with a center-hole SiC remoderator

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